Borehole testing method and apparatus



May 9, 1961 A. BLANCHARD 2,983,586

BOREHOLE TESTING METHOD AND PPARATUS Filed Nov. 7, 1957 2 Sheets-Sheet 1 FIGLI.

CONTROL cmculTs H IS ATTORNEYS May 9, 1961 A. BLANCHARD BOREHOLE TESTING METHOD AND APPARATUS Filed Nov. 7. 1957 FIGB.

2 Sheets-Sheet 2 INVENTOR ANDRE BLANCHARD gw@ J HIS ATTORN EYS MWL United States Patent BOREHOLE TESTIN G METHOD AND APPARATUS Andrev Blanchard, Houston, Tex., assignor to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Nov. 7, 1957, Ser. No. 695,071

14 Claims. (Cl. 12S- 230) The present invention relates to the detection of oxidizable materials in earth formations traversed by a borehole, and, more particularly, to novel and improved method and apparatuses for detecting the presence of the oxidizable materials in the earth formations, on the sides of which a mudcake or other similar material has formed, by exposing portions of the earth formations to the direct influence of an oxidizing agent.

Various systems and apparatuses have been developed for detecting the presence of oxidizable materials, such as petroliferous materials or hydrocarbons, in earth formations traversed by boreholes, in which it is intended that an oxidizing agent react with the petroliferous material or hydrocarbon when present in the earth formation under investigation, and that the results of this reaction be detected either thermometrically, chemically, by acoustical methods, or by pressure indicating devices in the case of an elastic wave generated by the reaction.

It has been intended that systems of this type would be very useful in determining the presence of oil, for example, in earth formations traversed by a borehole. However, it has been found that the known systems have not proved particularly successful owing to the difficulty of injecting the oxidizing agent through the mudcake formed on the sides of the borehole into the formation under investigation.

This difficulty may be readily overcome, in accordance with the invention, by causing fluids present in the earth formations under investigation to flush out and away the mudcake formed on the borehole wall adjacent the area under investigation. This is accomplished by isolating an area of the borehole wall including the adjacent mudcake and providing a space contiguous the isolated area in which the pressure is lower than the pressure of fluids within the formation under investigation. This lower pressure is maintained for as long a period as is necessary to permit iiuids from the formations under investigationto flush out the mudcake. An oxidizing agent capable of reacting with petroliferous material, hydrocarbons, or other oxidizable substances is introduced into a space contiguous with the then exposed portions of the earth formations at a pressure at least equal, and preferably somewhat higher than, the pressure of the fluids present within the earth formations so as to enable a detectable reaction to occur between the oxidizing agent and any petroliferous material, hydrocarbon, or other oxidizable material that may exist in the formation. The occurrence of the reaction is then preferably detected by differential thermometric means responsive to a differential increase in temperature between a point within the influence of the reaction and a relatively remote point outside the influence of the reaction.

In accordance with a preferred embodiment of the invention, a borehole tool is positioned opposite a particular formation under investigation and a sealing cup may be hydraulically forced against the mudcake and the formation. The sealing cup effects a sealing engagement Patented May 9, 1961 With the side of the borehole and acts to isolate an area of the borehole wall and the adjacent mudcake from any medium within the borehole and forms a space contiguous with the isolated area of the mudcake and formations. A reservoir, within or supported by the borehole tool and at a pressure lower than the expected pressure of fluids within the formation under investigation, is then opened to the space contiguous the isolated area. The differential pressure thus created across the mudcake permits the fluid in the formation to ilush out the mudcake into the reservoir. When sufficient mudcake has been flushed out, the space contiguous with the isolated area is then placed in communication with a. container for an oxidizing agent, such as perchloric acid, under a pressure at least equal to the pressure of the fluids in the formation so as to cause the oxidizing agent to enter the space and preferably permeate at least some of the exposed formation resulting in a reaction between the oxidizing agent and the oxidizable material from which is evolved a quantity of heat. A differential thermometric device, which may comprise, for example, a thermocouple having a junction in good thermal contact with the formation near the point of injection of the oxidizing agent and another thermocouple having a junction either imbedded in the same formation or mounted `on the borehole tool at a point close by but sufficiently relatively remote from the point of injection of the oxidizing agent as to be free of the effects of the induced thermal reaction, may be used to detect the `increase in temperature that will occur as a result of the reaction.

Por a more completely understanding of the applicants invention including various alternative embodiments, reference may be had to the following detailed description taken in conjunction with the accompanying figures of the drawing, in which:

Figure 1 is a schematic representation in partial longitudinal section of a borehole tool, constructed in accordance with an exemplary embodiment of the invention and positioned in a borehole adjacent a formation under investigation; and

Fig. 2 is a view in partial longitudinal section showing a portion of a borehole tool, constructed in accordance with `an alternate embodiment of the invention.

Referring to Fig. 1, a borehole tool 10 is supported by a conventional electrical conductor cable 11 in a borehole 12 containing borehole fluid 13 opposite an earth formation 14 containing fluids under pressure, hereinafter known as formation fluids. A mudcake 15 is formed on the side walls of the borehole 12. Such a mudcake usually forms in front of porous earth formations and renders the earth formations relatively inaccessible to testing techniques involving, for example, the use of fluids supplied from the borehole to either permeate or react with the earth formations.

The borehole tool 10 is positioned in and passed- -adjacent thereto. A space 23 is formed within the cup 22 and is sealed from the borehole fluid 13 by the edge of the cup 22 forming a seal with the mudcake and earth formations into which it is adapted to be pressed. In some cases, it may be desirable to use an inert, resilient, sealingedge or member either in conjunction with or as a substitute for the sealing cup 22 so as to improve the sealing action to be accomplished thereby.

When the borehole tool is positioned at a depth in theborehole opposite a particular earth formation which it isdesired to investigate, the sealing cup 22 may be forced into engagement with the side wall of the borehole by means of a hydraulically controlled back-up shoe 25, positioned diametrically opposite the sealing cup 22 on the side of the cylindrical housing 21. The back-up shoe 25 isset or retracted by two piston members 26 and 27 slidably fitted within `cylindrical recesses 28 and 2S, axially ldisposed and opening outwardly from the cylindrical housing 21.

The back-up shoe 2,5 is remotely controlled from the surface by means of an electrically controlled reversible pump 31 connected by means of electrical conductors 32, which may pass through a helical channel 34 around the outer surface of the housing 21, or other suitable means for carrying the conductors from the electrical instrument to the cable, and then through the cable 11 to the control circuits 18.

When the pump 31 is energized, it acts to pump noncompressible hydraulic uid from a reservoir 33 into the l cylindrical recesses 28 and 29, thereby forcing the backup shoe 25 away'from the housing 21 and against the adjacent .borehole wall. The -action of setting the backup shoe 25 causes the sealing cup 22 to be forced into sealing engagement with the mudcake and earth formations on the opposite wall. The back-up shoe 25 may be retracted in order to disengage the borehole tool 10 by causing the electrically reversible pump 31 to exhaust the non-compressible hydraulic fluid from the cylindrical recesses 2S and 29, thereby permitting suitable retracting springs 35 and 36 to return the piston arms land 27 of the back-up shoe 25 to a Withdrawn position within their respective cylindrical recesses.

The space 23 within the sealing cup 22 is connected by a passageway 38 and a passageway 39 to a reservoir 48 preferably located in the lower portion of the borehole tool 10. The effective volume of the reservoir 40 is controlled by 1a separator piston 41 freely oating on top of a cushion uid 42. The lower portion of the reservoir 40 is connected by means of an orifice 44 to a passageway 45 leading to a chamber 46 located below the reservoir 48 and at a pressure preferably of the order of amtospheric pressure. Fluid flow through the passageway is controlled by suitable valve means 48, such as a conventional electromagnetic, pressure-balanced, spring-loaded valve, which is adapted to be remotely controlled from the surface of the earth through electrical conductors 49 leading through the channel 34 and the cable 11 to the control circuit 18. Similarly flow through the passageway 39 is controlled by Suitable valve means 37, which may be of a conventional type such as shown in greater detail with respect to valve means 48, and which is also adapted to be remotely controlled through electrical conductors 47.

In order to determine the quantity of cushion Huid 42 that is permitted to flow through the orice 44 from the lower portion of the reservoir 48 to the chamber 46, al

differential pressure transducer 51, of conventional form, is hydraulically connected across the orifice means 44 by a passageway 50 leading to the opening to the orifice means 44, and by the passageway 45 connected to the output of the orifice means 44. An electrical signal rep- .resentative of the differential pressure across the orice within the, space23 ofthe sealing cup.22 until the pressure within the sealing cup 22 is substantially less than the pressure exerted by the formation fluids. This pressure differential results in aflow of formation fluids from the earth formations under investigation through the mudcake 15, causing the mudcake 15 to be flushed out of and away from the face of the earth formations and through the passages 38 and 39 to the reservoir 48. This ow will continue until the effective volume lof the reservoir 418 is substantially lled with mudcake and the formation uid. Thus the volumetric displacement of the cushion fluid 42 yfrom the reservoir 4t) is substantially equal to the amount of mudcake and formation fluid brought into the reservoir 4i). Accordingly, since the differential pressure transducer 51 provides an indcation of the amount of flow of cushion uid from the reservoir 40, a positive indication is had of the actual Volume of mudcake and formation fluid gathered in the reservoir 40 enabling the ,operator to know when the mudcake has been effectively removed from the formation and the time at which the valve 48 should be closed. Alternatively, the valves 37 and 48 may be automatically closed at the end of a predetermined time interval normally sufficient to permit the mudcake to be removed.

Following the ushing away of the mudcake from the face of the earth formation, it is necessary to inject an oxidizing agent, `for example, perchloric acid, into the space 23 of the sealing cup 22 so that the oxidizing agent may react with any oxidizable materials present in thepearth formation and preferably permeate at least a portion of the earth formation in the isolated area adjacent the sealing cup. This, in the embodiment of Fig. l, may be accomplished by a conventional metering pump comprising a piston 60 axially movable within a chamber 61 and having a metering stick `62 attached to one end thereof and adapted to control the effective volume of a metering chamber 63. The metering chamber 63 has an inlet connected through a ball check Valve 65 from a reservoir 66 containing the oxidizing agent 67. The metering chamber 63 also has an outlet passage through a ball check valve 69, a passageway 7i), and the passageway 38 to the space 23 in the sealing cup 22.

The movement of the metering pump is controlled by suitable means such as a four-way solenoid operated valve 72 remotely controlled from the surface through `the conductors 73 connected via the helical channel 34 and the cable 11 to the control circuits 18. When the four-way valve is deenergized, as shown in Fig. l, noncompressible hydraulic fluid from a fluid source including an hydraulic amplier 74, of conventional form, is in communication with that portion of the chamber 61 above the piston 60, and that portion of the chamber 61 below the piston 6l) is in communication with a suitable dump chamber 75. Under those conditions, the piston 66 is forced downwardly, pumping a predeterminedV quantity of the oxidizing agent present in the metering chamber 63 through its outlet passage into the space 23 adjacent the exposed earth formations. lt is intended that valve 37 be closed whenever oxidizing agent is being pumped from metering chamber 63 into space 23.

Upon energization of the four-way valve 72, the portion of the chamber 61 above the piston 6) of the metering .pump is placed in communication with the dump chamber 75 and the portion of the chamber 61 below the piston 60 is placed in communication with the hydraulic uidsource and hydraulic amplifier 74, thereby causing the piston 6l) to move in an upward direction, expanding the volume of the metering chamber 63 and resulting in the flow of a predetermined quantity of oxidizing agent 67 from the reservoir 66 through the ball check valve 65 into the metering chamber 63.

If oxidizable materials are present in the earth formations exposed to the oxidizing agent within the space 23 and permeating the earth formation, a reaction will take place involving the evolution of heat from the combus- .a differential thermometric device of conventional form having a thermocouple junction 76 supported within the space 23 at a point adjacent the earth formations subject to the injection of the oxidizing agent 67. A second i thermocouple junction 77 is carried by the back-up shoe and is embedded in the same formation at a point suciently relatively remote from the isolated area within In the alternate embodiment of the invention shown in Fig. 2, it is intended that the same basic arrangement may be utilized for causing the formation of fluids to flush away the mudcake from the face of the particular earth formation under investigation, and that the sealing cup 22 be held in sealing engagement with the wall of the borehole so as to form an isolated area in response to the operation of the back-up shoe 2S, in the same manner as is done in the embodiment shown in Fig. l. However, since the pressure of the mud colum within the borehole is normally in excess of the Huid pressures within the formation, the mud or borehole uid pressure may be utilized to inject the oxidizing agent into the exposed earth formation and the space 23 adjacent thereto. This may be accomplished by means of a reservoir 90 having a freely floating separator piston 91 mounted therein and adapted to float upon an oxidizing. agent 92 located in the bottom portion of the reservoir 90. The upper portion of the reservoir 90 is suitably sealed from the lower portion by the piston 91, but is exposed to and in communication with the borehole fluid 13 through an equalizing vent 93. An outlet for the reservoir 90' is provided at the bottom thereof through an orifice means 95 leading into a passageway 96. =Flow through the passageway 96 is controlled by suitable valve means, 97 such as an electromagnetic, pressure-balanced, springloaded valve, remotely controlled from the surface of the earth through conductors 9S leading through the helical channel 34 and the cable 11.

On indication as to the quantity of ilow of the oxidizing agent from the reservoir 90 is exhibited at the surface of the earth by means of a differential pressure transducer 99, for example, connected across the orifice means 95 by means of a passageway t100 connected to the mouth of the orifice means 95, and by the passageway 96 connected to the output of the orifice means 9S. Thus, when the mudcake has been flushed away from the isolated area adjacent the earth formation under investigation, the valve 97 can be opened to cause a selected amount of oxidizing agent to be injected by the borehole fluid pressure into the space 2.3 adjacent the exposed earth formation. An indication as to the differential temperature increase is then detected by the differential thermometric device including the thermocouples 76 and 77, as explained with relation to the embodiment of Fig. l.

ln the case of either embodiment, at the conclusion of the test, the back-up shoe 25 is retracted by operation of the electrically reversible pump 31 and retraction springs 35 and 36, and the borehole tool 10 is then pulled lose and repositioned for another test.

It will be obvious that the detection test that is accomplished by the disclosed apparatus in accordance with the invention may be performed a number of times without removing the borehole tool from the borehole, since the borehole tool can be moved from one level in the borehole to another desired level at which the back-up shoe 25 is then set, the mudcake is ushed away and the isolated earth formations are exposed to an oxidizing agent capable of causing a reaction with any oxidizable materials present in the earth formation.

Thus, there has been provided, in accordance with the invention, novel and improved method and apparatuses fordetecting the presence of oxidizable materials, such as petroliferous materials or hydrocarbons in earth formations traversed by a borehole on the sides of which a mudcake has been formed.

It will be understood by workers skilled in the art of investigating earth formations that the above embodiments are meant to be merely exemplary and that they are susceptible of modification and variation without departing from the spirit and scope of the invention. For example, instead of -using a reservoir with a separator piston exposed on one side to the pressure of the borehole liuid or mud within the borehole, a ilexible bag containing the oxidizing agent and exposed on its other side to the borehole fluid may be substituted for the separator piston. Such a bag would preferably be made :from an inert, resilient, thermoplastic material, such as a monochlorofluoroethylene polymer, which is unaffected by oxidizing agents such as perchloric acid in all concentrations, or temperatures up to approximately 300 F. Further, instead of using a diiferential thermometric device comprising a pair of spaced apart thermocouples, the temperature change may be measured by a differential resistance thermometer, or any other compact temperature sensing element. If desired, the sealing cup through which the oxidizing agent is fed into the earth formation may be separately movable relative to the elongated tool housing. For example, it may be on or part of a slidably attached shoe that is driven in any known manner toward the wall of the borehole and retracted after the completion of a test. Therefore, the invention is not deemed to be limited except as defined by the appended claims.

I claim:

l. A method for detecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising the steps of isolating an area of the borehole wall including any mudcake adjacent thereto, opening said isolated area to an enclosed volume at a pressure on the order of atmospheric pressure thereby selectively causing the uids present in the earth formations adjacent the isolated area to flush the mudcake away from said isolated area of the borehole wall and into an area removed Afrom said isolated area, introducing after removal of the mudcake an oxidizing agent capable of reacting with oxidizable materials in the earth formations into a space contiguous with exposed portions of said earth formations in the isolated area of the borehole wall at a pressure at least equal to the pressure of the fluids present in the earth formations` so as to cause a detectable reaction between said oxidizing agent and any oxidizable materials present in said formation, and providing an indication of the occurrence of the reaction.

2. A method -including the steps set forth in claim l, wherein an indication of the occurrence of the reaction is provided in response to the detection of an increase in the differential temperature between a point within the area of influence of said reaction and a :relatively remote point substantially outside the area of inuence of said reaction.

3. A method for detecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising the steps of isolating an area of the borehole wall including any mudcake adjacent thereto, selectively establishing in a space contiguous with said isolated area a `pressure on the order of atmospheric pressure and substa-ntially less than the pressure of fluids present in the earth formations adjacent the isolated area so as to cause said fluids to flush the mudcake out of and away from said isolated area of the borehole wall and into an area removed from said isolated area, subsequently introducing after removal of the mudcake an oxidizing agent capable of reacting with oxidizable materials in the earth formations into said space at a pressure at least equal to the pressure of the fluid present in the earth formations so .as Ato cause adetectable reaction between said oxidizing agent and any oxidizable materialspresent in said formation, and detecting an increase in temperature of a point within the area of influence of said detectable reaction representative of the occurrence of such a reaction.

4. A method fordetecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprisingthe steps of isolating an area of the borehole wall including any mudcake adjacent thereto, selectively creating a pressure within a space contiguous with said isolated area of a magnitude on the-order of atmospheric pressure and suiciently less than the pressure of fluids present in the earth formations adjacent the isolated area to cause said iiuids to flush out and away themudcake from said isolated. area of the borehole wall and into an area removed from said isolated area, maintaining the ow of fluids from said formation for a period of time suiiicient to remove enough mudcake from said isolated area to expose at least some portions of said adjacent earth formations to contact with substances introduced into said space, subsequently introducing after removal of the mudcake a predetermined quantity of an oxidizing agent capable of reacting with oxidizable materials in the earth formations into said space contiguous with the exposed portions of said earth formations in the isolated area of the `borehole wall at a pressureat least equal to the pressure of the lluids present in the earth formations so as to cause a detectable reaction between said oxidizing agent and any oxidizable materials present in said formation, detecting an increase in temperature at a point within the influence of said reaction and resulting therefrom, and providing an indication of said temperature increase representatiVe-of the presence of oxidizable materials in the particular earth formations under investigation.

5. An apparatus for detecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising a housing adapted to be passed through the borehole and positioned opposite an earth formation under investigation, isolating means carried by said housing and including a hollow portion opening toward and having edges adapted to engage the side wall of said borehole adjacent an earth formation under investigation, means for selectively uring said edges of said hollow portion of said isolating means into sealing engagement with said borehole wall so as to isolate the portion of said borehole wall included within said edges, reservoir means carried by said housing and in communication with a space formed within said hollow portion of said isolating means for receiving mudcake and formation fluids therefrom, means for selectively creating a pressure on the order of atmospheric pressure within said hollow portion space and substantially less than the pressure uids present in the earth formations adjacent said isolated portion of said borehole wall, thereby causing said formation fluids to liush said mudcake out of and away from said earth formations and into said reservoir means, means for supplying an' oxidizing agent capable of reacting with oxidizable materials in the earth formations, means for injecting after removal of the mudcake a predetermined amount of said oxidizing agent into said hollow portion space of said isolating means, and means located within said space and adapted to be inliuenced by a thermal reaction in said adjacent earth formations for detecting an increase in temperature resulting from the reaction of said oxidizing agent with any oxidizable materials present in said earth formation.

6. An apparatus for detecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising a housing adapted to be passed through the borehole and ,positioned opposite an earth formation under investiga- `tion, isolating means carried by said housing and including ahollowfportion Vopening toward and'lhaving edges adapted to engage the side wall of said borehole adjacent an earth formation under investigation, means for selectively urging said edges of said hollow portion of said isolating means into engagement with said borehole wall so as to isolate the portion of said borehole wall Vincluded within said edges, variable volume reservoir means carried by said housing and in communication with a space formed within said hollow portion of said isolating means for receiving mudcake and formation fluids therefrom, means for controlling the volume of said reservoir means so as to create a pressure within said hollow portion sp-ace on the order of atmospheric pressure and substantially less than the pressure of fluids present in the earth formations adjacent said isolated portion of said borehole wall, thereby causing said formation fluids to flush said mudcake out of and away from said earth formations and i-nto said reservoir means, means whereby said liushing of the mudcake into said reservoir means is selectively accomplished, means for supplying an oxidizing agent capable of reacting with oxidizable materials in the earth formations, means for injecting after removal of said mudcake a predetermined amount of said oxidizing agent into said hollow portion space of said isolating means, and means located within said hollow portion space and adapted to be influenced by a thermal reaction in said adjacent earth formation for detecting an increase in temperature resulting from the reaction of said oxidizing agent with any oxidizable materials present in said earth formation.

7. An apparatus for detecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising a housing adapted to be passed through the borehole and `positioned opposite an earth formation under investigation, isolating means carried by said housing and including a hollow portion opening toward and having edges adapted to engage the side wall of said borehole adjacent an earth formation under investigation, means for selectively urging said edges of said hollow portion of said isolating means into sealing engagement with said borehole wall so as to isolate the portion of said borehole Vwall included within said edges, variable volume reservoir means carried by said housing and having an upper variable volume chamber communication with a space formed Within said hollow portion of said isolating means for receiving mudcake and formation iiuids therefrom, and -displaceable piston means `operable to control the volume of said upper chamber, means for controlling said displeaceable piston means to create a pressure on the order of atmospheric pressure within said upper chamber and said hollow portion space and substantially less than the pressure of fluids present in the earth formations adjacent said isolated portion of said borehole wall, thereby causing said formation fluids to flush said mudcake out of and away from said earth formations and into said reservoir means, means whereby said flushing of the mudcake into said reservoir means is selectively accomplished, means for supplying an oxidizing agent capable of reacting with oxidizable materials in the earth formations, means for injecting after removal of said mudcake a predetermined amount of said oxidizing agent into said hollow portion space of said isolating means, and means located within said hollow portion space and adapted to be inuenced by a thermal reaction in said adjacent earth formations for detecting an increase in temperature resulting from the reaction of said oxidizing agent with any oxidizable material present in said earth formation.

8. An apparatus for detecting the presence of oxidizable materials in earth formations traversed by a borehole `on the sides of which mudcake has formed, comprising a housing adapted to be passed through the borehole and positioned opposite an earth yformation under investigation, isolating means carried by said housing and in- -cluding a--hollow portion opening toward and having `edges adapted to engage the side wall of said borehole adjacent an earth formation under investigation, means for selectively urging said edges of said hollow portion of said isolating means into sealing engagement with said borehole Wall so as to isolate the portion of said borehole wall included within said edges, variable volume reservoir means carried by said housing and having an upper chamber in communication with a space Iformed within said hollow portion of said isolating means vfor receiving mudcake and formation lluids therefrom, a lower chamber containing cushioning fluid and a floating piston dirposed therebetween, means including a reservoir at a pressure on the order of atmospheric pressure and choke means therefor for controlling the quantity of cushioning fluid in said lower chamber of said variable volume reservoir means to control the position of said piston thereby varying the volume of said upper chamber and including valve means arranged so as to selectively estab lish a pressure within said upper chamber and said hollow portion space of said isolating means substantially less than the pressure of fluids present in the earth forma` tions adjacent said isolated portion of said borehole wall and causing said formation fluids to flush said mudcake out of and away from said earth formations and into said reservoir means, means Ifor supplying an oxidizing agent capable of reacting with oxidizable materials in the earth formations, means for injecting after removal of said mudcake a predetermined amount of said oxidizing agent into said hollow portion space of said isolating means, and means located within said hollow portion space and adapted to be influenced by a thermal reaction in said adjacent earth formations for detecting an increase in temperature resulting from the reaction of said oxidizing agent with any oxidizable materials present in said earth formation.

9. An apparatus for detecting the presence of oxidizable materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising a housing adapted to be passed through the borehole and positioned opposite an earth formation under investigation, isolating means carried by said housing and including a hollow portion opening toward and having edges adapted to engage the side Wall of said borehole adjacent an earth formation under investigation, means for selectively urging said edges of said hollow portion of said isolating means into sealing engagement with said boreholewall so as to isolate the portion of said borehole wall included within said edges, variable volume reservoir means carried by said housing and including piston means for separating said reservoir means into an upper chamber and a lower chamber, each of variable volume, said upper chamber being in communication with a space 'formed within said hollow portion of said isolating means for receiving mudcake and formation fluids therefrom, said lower chamber containing a cushioning fluid for supporting said piston means, means including a reservoirl at a pressure on the order of atmospheric pressure and choke means therefor for withdrawing cushioning fluid from said lower chamber of said variable volume reservoir means to increase the volume of said upper chamber of said variable volume reservoir means, thereby creating a pressure within said upper chamber and said hollow portion space of said isolating means substantially less than the pressure of fluids present in the earth Vformations adjacent said isolated portion of said borehole wall and causing said formation fluids to flush said mudcake out of and away `from said earth formations and into said reservoir means, valve means whereby said flushing of the mudcake into said reservoir means is selectively accomplished, means for measuring the amount of cushioning iluid withdrawn yfrom said lower chamber of said variable volume reservoir means, said amount of cushioning fluid withdrawn from said lower chamber being representative of the amount of said mudcake and said formation uids received in said upper chamber, means for by a thermal reaction in said adjacent earth formations for `detecting -an increase in temperature resulting from the reaction of said oxidizing agent with any oxidizable materials present in said earth formation.

10. Apparatus as described in claim 9, wherein said means for supplying an oxidizing agent comprises a reservoir means carried by said housing, and said means for injecting a predetermined amount of said oxidizing agent .into said hollow portion of said isolating means comprises selectively controllable pumping means for withdrawing a predetermined amount of said oxidizing agent from said reservoir means and for injecting said predetermined amount of said oxidizing agent i-nto said hollow portion space of said isolating means.

l1. Apparatus as described in claim 9, wherein said means 4for supplying an oxidizing agent comprises second variable volume reservoir means containing said oxidizing agent and being responsive to the ambient pressure within the borehole surrounding said housing so as to maintain said oxidizing agent at said ambient pressure; and said means for injecting a predetermined amount of said oxidizing agent into said 4hollow portion space of said isolating means comprising means for selectively permitting flow of said oxidizing agent from said second reservoir means into said hollow portion space of said isolating means and means `for measuring the volume of said oxidizing agent passing from said second reservoir means into said hollow portion space.

12. `Apparatus as defined in claim ll, wherein said second variable volume reservoir means includes an upper chamber and a lower chamber, said lower chamber containing said oxidizing agent, and displaceable piston means separating said upper and lower chambers and supported by said oxidizing agent in said lower chamber, said upper chamber of said second variable volume reservoir means being in communication with the interior of said borehole surrounding said housing so that said piston means of said second variable reservoir means is subject to ambient pressure conditions in said borehole.

13. A method for the exploration of materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising the steps of isolating an area of the borehole wall including any mudcake adjacent thereto, `selectively opening said isolated area to an enclosed volume at a pressure on the order of atmospheric pressure thereby causing the fluids present in the earth formations adjacent the isolated area to flush the mudcake away from said isolated area of the borehole wall and into an area removed from said isolated area, introducing after removal of said mudcake an agent capable of aifecting a characteristic of the materials in the earth Kformations into a space contiguous with exposed portions of said earth 'formations in the isolated area of the borehole wall at a pressure at least equal to the pressure of the iluid present in the earth formations, and detecting said characteristic of said materials after exposure to said agent.

14. An apparatus for the exploration of materials in earth formations traversed by a borehole on the sides of which mudcake has formed, comprising a housing adapted to be passed through the borehole and positioned opposite an earth formation under investigation, isolating means carried by said housing and including a hollow portion opening toward and having edges adapted to engage the side wall of said borehole adjacent an earth formation under investigation, means for selectively urging said edges of said hollow portion of said isolating means into sealing engagement with said borehole wall so as to isolate the portion of said borehole wall included within said edges, reservoir means carried by said housing and in communication with a space formed within said hollow portion of said isolating means -for receiving mudcake and yformation iluids therefrom, means for selectively creating a pressure on the order of atmospheric pressure within said hollow portion and substantially less than the pressure of `fluids present inthe earth formations adjacent said isolated portion of said borehole wall, thereby causing said formation fluids to tlush said mudcake out of and away Ifrom said earth formations and into said reservoir means, means for supplying an agent capable of aiecting a characteristic of the materials in the earth formations, means for injecting after removal of said mudcake a predetermined amount of said agent into said hollow portion of said isolating means, and means for detecting said characteristic of said materials after eX- posure to said agent.

References Cited in the le of this patent UNITED STATES PATENTS Disclaimer 2,983,586.And1"e Blcmcwmd, Houston, Tex. BOREHOLE TESTING METHOD AND APPARATUS. Patent dated May `9, 1961. Dsclaimer led Jan. 5, 1965, by the assignee, Schlumbevge?" Well Swweyng Uowpo'rcm'on.

1er to claims 3 and 4 of said patent.

Hereby enters this disdain [Oaz'al Gazette Apm'l 13,1965.]

Notice of Adverse Decision in nterference In Interference No. 93,017 involving Patent No. 2,988,586, A. Blanchard, Borehole testing method and apparatus, nal judgment adverse to the patentee was rendered Oct. 15, 1964:, as t0 claims 3 and 4.

[Oez'al Gazette Deeembeqa Z2, 1964.] 

1. A METHOD FOR DETECTING THE PRESENCE OF OXIDIZABLE MATERIALS IN EARTH FORMATIONS TRAVERSED BY A BOREHOLE ON THE SIDES OF WHICH MUDCAKE HAS FORMED, COMPRISING THE STEPS OF ISOLATING AN AREA OF THE BOREHOLE WALL INCLUDING ANY MUDCAKE ADJACENT THERETO, OPENING SAID ISOLATED AREA TO AN ENCLOSED VOLUME AT A PRESSURE ON THE ORDER OF ATMOSPHERIC PRESSURE THEREBY SELECTIVELY CAUSING THE FLUIDS PRESENT IN THE EARTH FORMATIONS ADJACENT THE ISOLATED AREA TO FLUSH THE MUDCAKE AWAY FROM SAID ISOLATED AREA OF THE BOREHOLE WALL AND INTO AN AREA REMOVED FROM SAID ISOLATED AREA, INTRODUCING AFTER REMOVAL OF THE MUDCAKE AN OXIDIZING AGENT CAPABLE OF REACTING WITH OXIDIZABLE MATERIALS IN THE EARTH FORMATIONS INTO A SPACE CONTIGUOUS WITH EXPOSED PORTIONS OF SAID EARTH FORMATIONS IN THE ISOLATED AREA OF THE BOREHOLE WALL AT A PRESSURE AT LEAST EQUAL TO THE PRESSURE OF THE FLUIDS PRESENT IN THE EARTH FORMATIONS SO AS TO CAUSE A DETECTABLE REACTION BETWEEN SAID OXIDIZING AGENT AND ANY OXIDIZABLE MATERIALS PRESENT IN SAID FORMATION, AND PROVIDING AN INDICATION OF THE OCCURRENCE OF THE REACTION. 